The present invention relates generally to the field of biochemical analysis, and in particular to a cartridge for analyzing a fluid sample.
The analysis of clinical or environmental fluid samples generally involves a series of chemical, optical, electrical, mechanical, or thermal processing steps on the samples. In recent years, there has been growing interest in developing disposable cartridges for conducting analyses of biological samples for various diagnostic and monitoring purposes. For example, U.S. Pat. No. 5,587,128 to Wilding discloses devices for amplifying a preselected polynucleotide in a sample by conducting a polynucleotide amplification reaction. U.S. Pat. No. 5,922,591 to Anderson et al. describes a miniaturized, integrated nucleic acid diagnostic device and system. The device is generally capable of performing one or more sample acquisition and preparation operations, in combination with one or more sample analysis operations.
Prior fluidic cartridges for processing fluid samples have focused on picoliter, nanoliter, and microliter sample volumes. These small sample volumes are not practical for many realistic diagnostic applications. Of special interest is the detection of target analytes (e.g., nucleic acid) that exist in low concentrations in many samples. For example, in detecting infectious diseases, gram negative bacteria can be present at less than 10 copies per milliliter of blood, cryptosporidium generally appears as only a few copies per gallon of drinking water, concentrated biothreat agents (e.g., anthrax) at less than 100 copies per milliliter of water, and food poisoning agents, such as E. coli and salmonella, may be manifested in less than 10 copies per gram of food.
The present invention provides a cartridge for analyzing a fluid sample, e.g., to determine the presence or absence of an analyte in the sample. The desired analyte is typically intracellular material (e.g., nucleic acid, proteins, carbohydrates, lipids, bacteria, or intracellular parasites). In a preferred use, the analyte is nucleic acid which the cartridge separates from the fluid sample and holds for amplification (e.g., using PCR) and optical detection.
In a preferred embodiment, the cartridge has a sample port for introducing a sample into the cartridge, and a sample flow path extending from the sample port. The cartridge also has a lysing chamber in the sample flow path. The lysing chamber contains at least one filter for capturing cells or viruses from the sample as the sample flows through the lysing chamber. Beads are also disposed in the lysing chamber for rupturing the cells or viruses to release the analyte therefrom. The cartridge also includes a waste chamber in fluid communication with the lysing chamber via the sample flow path for receiving the remaining sample after the sample flows through the lysing chamber. The cartridge further includes an analyte flow path extending from the lysing chamber. The analyte flow path diverges from the sample flow path. In the preferred embodiment, the analyte flow path leads to a reaction chamber for chemically reacting and optically detecting the analyte. The cartridge also includes at least one flow controller (e.g., valves) for directing the sample into the waste chamber after the sample flows through the lysing chamber and for directing the analyte separated from the sample into the analyte flow path.
The cartridge includes one or more membrane-type valves to direct fluid flow. The valves permit efficient processing of large sample volumes to enable the accurate detection of low concentration analytes. In first embodiment, the cartridge comprises a body defining at least first and second channels and a conical valve seat positioned between the channels. The cartridge also comprises an elastic membrane for establishing a circular seal with the valve seat to prevent the flow of fluid between the channels. The cartridge optionally comprises a valve actuator and an elastic body for forcing the valve actuator to press the membrane against the valve seat. The valve actuator has a spherical surface for pressing the membrane against the conical valve seat. Alternatively, the valve actuator and/or elastic body may be located in an instrument into which the cartridge is inserted for sample processing.
In a second embodiment, the cartridge comprises a body having formed therein a chamber, a conical valve seat in fluid communication with the chamber, and a channel extending from the valve seat. The cartridge also comprises an elastic membrane for establishing a circular seal with the valve seat to prevent the flow of fluid between the chamber and the channel. The valve seat is preferably in fluid communication with the chamber via a port or channel intersecting the center of the valve seat. The cartridge optionally comprises a valve actuator and an elastic body for forcing the valve actuator to press the membrane against the valve seat. The valve actuator has a spherical surface for pressing the membrane against the valve seat. Alternatively, the valve actuator and/or elastic body may be located in an instrument into which the cartridge is inserted for sample processing.
In a third embodiment, the cartridge comprises a body defining at least first and second channels and a cavity separating the channels. An end of the first channel is positioned on a first side of the cavity, and an end of the second channel is positioned on a second side of the cavity. The cavity is defined by a first curved surface positioned adjacent the end of the first channel, a second curved surface positioned adjacent the end of the second channel, and at least a third surface between the first and second curved surfaces. The cartridge also comprises an elastic membrane for establishing a seal with the first and second curved surfaces to prevent the flow of fluid between the channels. The third surface is recessed from the first and second surfaces to provide a gap between the membrane and the third surface when the membrane is pressed against the first and second surfaces. The first and second curved surfaces preferably comprise first and second concentric spherical surfaces. The cartridge optionally comprises a valve actuator having a third spherical surface for pressing the membrane against the first and second spherical surfaces. Each of the first and second spherical surfaces preferably has a radius of curvature substantially equal to the sum of the radius of curvature of the third spherical surface plus the thickness of the membrane. The cartridge may also include an elastic body for forcing the valve actuator to press the membrane against the first and second spherical surfaces. Alternatively, the valve actuator and/or elastic body may be located in an instrument into which the cartridge is inserted for sample processing.